1. Field of the Invention
The present invention relates to holders for wound film mate is such as microfilm, and more particularly to film retention cores utilized therein. Still more particularly, the present invention relates to a film retention core structured for providing both easy loading and tenacious film retention.
2. Description of the Prior Art
It is known to provide structures of holding wound film materials. These structures, known as film holders, are composed of a reel having two separated discs and a central core which connects with each of the discs and affords a structure for holding an initial section of the film material from unraveling from the reel holder.
One example of a wound film material holding structure is represented by a product currently on the market which is depicted in FIG. 1 and described in U.S. Pat. No. 4,798,352 to Naso et al, dated Jan. 17, 1989. In this film holder 200, there is provided a reel consisting of a pair of separated top and bottom discs 202, 204 and a core 206 connecting the discs. The core 206 has an outer collar 208 and an inner collar 210 between which is formed a thread-space 212. The thread-space communicates with a slot 214 provided in the top disc 202 and the outer collar 208. A plurality of convex surfaces 216 are connected with the inner collar 210. There is also provided a rib 218 connected with the outer collar 208 and a post 220 connected with a floor 222 of the core 206. In operation, the film 224 is looped and then threaded labyrinthly around the convex surfaces, rib and the post,
Another example of a wound film material holding structure is represented by another product currently on the market which is depicted in FIG. 2 and described in U.S. Pat. No. 4,540,134 to Schankler, dated Sep. 10, 1985. In this film holder 300, there is provided a reel consisting of a pair of separated top and bottom discs 302, 304 and a core 306 connecting the discs. The core 306 has a cylinder 308 and a collar 310 between which is formed a thread-space 312. The thread-space communicates with a slot 314 provided in the top disc 302 and the cylinder 308. The collar is rectangular with a plurality of corners 316 whereat there is an opposed rib 318. There is further provided a channelled wall member 320 connected with the collar with an opposing rib 318. A post 322 is connected with a floor 324 of the core 306. A rib 326 is connected with the collar 310 adjacent the post 322. In operation, the film 328 is looped and then threaded labyrinthly between the corners and ribs, the channelled wall member and its adjacent rib, and the post.
Both of these structures suffer from widely separated interacting adjacent film abutments which pose difficult threading for a user. Further, since the interacting adjacent film abutments are mutually widely spaced, there is the potential for generation of untoward strain in the film at these abutments which can lead to failure of the film.
Accordingly, what is needed is a core for film reels which affords very easy loading of the film, long life for the film, and excellent retention of the film with respect to the core.